Radomsko (pronounced [raˈdɔmskɔ] ^ⓘ) is a city in central Poland with 44,700 inhabitants (2021). It is situated on the Radomka river in the Łódź Voivodeship. It is the county seat of Radomsko County.

Founded in the 11th century, Radomsko is a former royal city located within the Sieradz Land, which prospered as a trade center due to its location at the intersection of important trade routes. In the 14th century, it was the site of congresses at which Princess Jadwiga of Poland was chosen as Queen of Poland as the country's first female monarch. Due to particularly strong partisan resistance against German occupiers during World War II, it was dubbed Banditenstadt ("City of Bandits") by the Germans.

It is located on the main railway line connecting Warsaw and Katowice, the country's two largest metropolitan areas, and on the main highway connecting Gdańsk and Łódź with Katowice, part of the European route E75.

Radomsko dates back to the 11th century. The oldest known mention of Radomsko comes from a document of Konrad I of Masovia from 1243. It received town privileges from Duke Leszek II the Black of Sieradz in 1266. During the times of fragmentation of Piast-ruled Poland, it was part of the Seniorate Province and Duchy of Sieradz, and afterwards it was a county seat and royal town of the Kingdom of Poland, administratively located in the Sieradz Voivodeship in the Greater Poland Province. In 1288, Duke Leszek II the Black brought Franciscans to the town, and in 1328, King Ladislaus the Short funded the construction of the Gothic Franciscan church.

In 1382 and 1384, congresses of Polish nobility were held in Radomsko, during which Princess Jadwiga of Poland was chosen as Queen of Poland as the country's first female monarch. It was probably Radomsko where an agreement was concluded under which the future king of Poland Władysław II Jagiełło married Jadwiga, hence founding the Jagiellonian dynasty. Nowadays, Queen Jadwiga is considered the patron saint of Radomsko. The town developed under the patronage of the Jagiellonian dynasty, and was granted important trade and tax privileges by Kings Władysław II Jagiełło in 1427 and Sigismund II Augustus in 1549 and 1552.

In 1793 as a consequence of the Second Partition of Poland the town became part of the Kingdom of Prussia. In 1807 it became part of the Polish Duchy of Warsaw, then in 1815 part of Congress Poland within the Russian Empire. In 1846 the section of the Warsaw–Vienna railway that ran through the town opened, providing a railway connection to Warsaw. Inhabitants took part in the November and January uprisings against Russia. One of the first battles of the Polish January Uprising in the region took place in Radomsko on January 24, 1863. Further clashes between Polish insurgents and Russian troops took place in Radomsko on March 14 and June 24, 1863. After the fall of the January Uprising, anti-Polish repressions, including Russification policies, intensified. The Russian administration expelled Franciscan monks from the town.

During World War I, the town was occupied by Austria. On 7 November 1918, local inhabitants and members of the secret Polish Military Organisation disarmed the Austrians and liberated the town, four days before Poland officially regained independence. Polish political prisoners were then released. The Franciscans came back to their monastery in 1918.

On 1 September 1939, the first day of the German invasion of Poland that started World War II, the Germans air raided the town. Dozens of civilians were killed in the bombings. Radomsko was taken over by the Wehrmacht on 3 September 1939. The next day, the Germans carried out executions of Poles in the present-day districts of Bartodzieje, Folwarki and Stobiecko Miejskie. On 6–8 September 1939, the Einsatzgruppe II entered the town, and then carried out mass arrests of Poles, and searched Polish offices and organizations. Polish underground resistance was organized already in October 1939. There was also secret Polish schooling.